Metal drawing press



Ressued Aug. 4, 1942 UNITED lSTATE METAL DRAWING PRESS Walter Ernst, Mount Gilead, Ohio, assigner to The Hydraulic Development Corporation, Inc., Wilmington, Del., a corporation of Delaware Original No. 2,214,635, dated September 10, 1940, Serial No. 153,157, July 12, 1937, which is a division of Serial No. 101,110, September 16, 1936, now Patent No. 2,167,941, dated August 1, 1939. Application for reissue August 2, 1941,

Serial No. 405,248

12 claims. (ci. 11s-4s) f l This invention relates to presses and, inparticular, tohydraullc presses having blankholding arrangements in association with drawing devices.

One object oi' this invention is to provide a hydraulic press having a drawing plunger and a plurality of clamping plungers. operating in drawing and clamping cylinders, respectively, the pressure for operating the clamping cylinders being provided by the action of the drawing plunger in forcing the clamping plungers downwardly against the blank, means being provided for releasing pressure fluid from the diierent Aclamping cylinders at different predetermined pressures so as to enable the blank to be held at diiferent'points by diiIerent clamping pressures.

Another object is to providea hydraulic press having a drawing plunger and a plurality of clamping plungers arranged to provide dinerent clamping pressures among themselves, together with release of pressure fluid therefrom on lthe attainment of diiIerent predetermined pressures therein, means being provided to prevent the escape of pressure fluid lupon'the return stroke of the drawing plunger when the pressure-releasing means is set at a low amount, thereby counteracting the eifect of the pressure-releasing means .during the return stroke of the press.

This is s. division of my copending application, Ser. No. 101,110, filed September 16, 1936, now Patent 2,167,941,Aug. 1, 1939.

In the drawing:

Figure 1 is a diagrammatic view, mainly in section, showing the working elements of a hydraulic press` circuit arranged according to this invention, with the upper portion of the press ization of pressure between the different clamping cylinders by' the discharges from their relief valves. `The arrangement of Figure l also contains a provision whereby the action of the various relief valves is prevented during the return stroke by admitting fluid to the opposite .side of the valve plunger, this arrangement enabling the moving parts to return on thereturn stroke, regardless of how low the relief valve setting may be.

The reason for providing a different clamping pressure at diiferent portions of the blank arises from the fact that it is 4found that in drawing irregular work pieces'it is often desirable to hold one portion ofA the periphery of the blank with a tighter clamping force than other portions. In the ordinary types of presses, wherein the .same clamping pressure isprovided on all portions of the blank, this variable blank-holding force cannot be supplied. In the present invention,'however, each individual clamping cylinder y is equipped with its own relief valve and its own check valve so that a different clamping pressurecan bebuilt up on each one of the several clamping plungers.

' Referring to the drawing in detail, Figure 1 shows diagrammatically a hydraulic metall drawing press having a base member il connected to a top member Il (reduced in size for clearness of showing) by means of tie rods I2, the latter being secured in position by means of the v nuts I3 upon the endsthereof. Mounted in the framework omitted to show the construction more clearly'.

Figure 2 is a Horizontal section along the line 2-2 in Figure l.

Figure 3 is a vertical section through a pressure relief valve employed in connectlonwith the press circuit shown in Figure`1.

In general, the press of this invention con-. sists of a drawing plunger and a plurality of clamping plungers having relief `valves associ- -ated with each clamping plunger for release of the pressure iiuid therein at predetermined pressures, thereby enabling the 'different clamping plungers to exert different clamping pressures upon the blank. There is also provided a series of check valves adapted to prevent the individual relief valves from interfering with the action of -each other, thereby preventing equalbase member III is a drawing die I4 having a die cavity I5 for receiving the blank Il. Assoelated with the die cavity I9 is a plunger i'l adapted to support the tip of the blank as it is being drawn, and passing through a bore IB to its operating cylinder (notshown). The de' tails of the supporting plunger I1 form no part of-the present invention, and are shown'in my copending application, Ser.V No. 74,742, filed AprilV 16, 1936, which has matured to Patent No. 2,136,- 240, issued November 8, 1938.

The present inventionl may be employed either with fiat blanks or -with blanks which have a1- ready been subjected to one or more drawing operations. For convenience of disclosure, blank I6 is shown as' having been subjected to one drawing operation, and in position for another drawing operation,'which will elongate itv and cause it to be drawn downwardly irto the die cavity I5. f

Associated with the top member Il of the press is a surge tank i9 for containing the fluid by which the press is actuated. Also associated with the top-member II is the drawing or main cylinder 20, having a bore 2| within which reciprocates the double-acting drawing-plunger 22 having a piston head 23 thereon. The cylinder 25 is .provided with upper and lower ports 24 and 25, on opposite sides of the piston head 23, and adapted by means of pipes 25 and V21'to supply pressure fluid to advance orretract the drawing plunger 22, according to themanner in which the four-way" valve 2li is lmanlpulated. 'I'his valve 28 is of any suitable type known to those skilled in 4the art, and its 4details form no part of the present invention.

. pressure relief valve 5I and safety valve 55 so each clamping cylinder is provided with its own that a different pressure release point may be given to each clamping cylinder. The pressure Arelief valves 5I'are connected to the drawing plunger passageway 41 by conduits 55 for the tion with the description of the details' of th Y relief valve Il.

Leading from the four-way valve 25 is thepressure line 29 connected at its opposite end to the pump 35. A discharge line 3l, also connected to the four-way valve 28, leads into the interior of the surge tank I9. 'I'he pump 35 is also provided with a suction line 32, likewise leading into the interior of the surge tank I9.

mouth of its bore 2| with a packing ring 33, beyond which is a packing 34 adapted to be compressed by -a gland 35 so as to prevent leakage around the drawing plunger 22. Connected to the drawing plunger 22 is the platen 35, within which are arranged the clamping cylinders 31 having clamping plungers 38 operating therein. Each clamping plunger 35 is provided with a packing 39 and gland 40 for the |prevention of leakage. Secured to the platen 35 is a drawing plunger or punch 4| having a nose portion 42 corresponding to the die cavity I5, and adapted to pass through an aperture 43 in the clamping member 44 secured to the outer ends of the clamping plungers 38.

Each of the clam-ping cylinders 31 is provided 'with a iluld passageway 45 leading by way of an outwardly opening check valve 45 to a common passageway 41, which extends upwardly through the drawing plunger 42 and opens into the dra'wingcylinder bore 2| immediately beneath the drawing plunger head 23. Consequently, fluid is free to pass from the pull-back or return side of the drawing plunger 23 into the clamping cyl' inders 31, butis-prevented from passing in the opposite direction by the action of the check valves A45. VAlso passing outwardly from each clamping cylinder 31 is a fluid conduit 48 leading to an intermediate portion of a pipe 49, having on one endV a safety valve 55 and on the. other end a pressure relief valve 5|. Leading from the discharge side-of the safety valve 55 is a discharge line 52 connected to the discharge side f the relief valve 5I by the line 53.

The discharge line 52 passes upwardly into the telescopic cylinder 54, thereby forming a slip connection, enabling the telescoping cylinder 54 and the pipe 52 to move vertically relatively to' each other, an action which necessarily occurs when the [platen 55 moves downwardly in response tothe action of the drawing plunger 22. A dischargeline 55 leads `from the telescoping cylinder 54 into the interior of the surge tank Iland serves to discharge uid expelled from the-pressure relief valve ofthe safety valve 55.l The safety valve 50 is provided merely as an additional safety feature in the event of a jamming or other failure ofy th pressure relief valve 5I, and is set at a higher pressure than the relief va1ve5|soastooperateincasooftheaccumulation of a dangerous pressure 'within the corresponding clamping cylinder 31 and a failure of thecorresponding pressure relief valve 5I to The drawing cylinder is Ysupplied near the The reliefvalve 5| isrshowndn vertical section in Figure 3, and consists Aof a casing 50 having a .bore 5I within which reciprocates a valve plunger 52. Arranged between the valve plunger 52 and the bore 6I is a tubular-member 53 having a longitudinalbore 65 and a cross bore 58 engaging the threaded portion 59 of the casing 65, whereas the end of the pipe 53 is similarly held in communication with the transverse bore 51 by means of the threaded collar 1|) engaging the threadedportion 1|- of the casing (Figure Mounted on. the upper portion of the Vcasing 55 is a tubular cap 12 secured thereto by screws 13. Within the cap 12 is a coil spring 14, one

end of which engages an enlargement 15 upon the upper end of the valve plunger 52, whereas the opposite end engages a button 16 in contact with an adjusting screw 11 threaded through a bore 13 in the upper end ofthe cap12. Surrounding and covering the adjusting screw 11 is a hollow nut 19 which serves to. protect the ad-4 justing screw 11 and also to lock it in its adjusted position. The cap 12 is provided with a port 55 receiving and communicating with the pipe 55 leading .to the pull-back side of the drawing plunger 22, as shown in Figure 1.

Thus, when the same pressure iuid is admitted simultaneously to the valve 5|, by way of the pipes 49 and 55 during the pull-back stroke of the press, the valve plunger 52 will beprevented from opening by means of this counteracting arrangement, as is more fully described under the operation thereof. The pipe 5.a1so serves during the return stroke of the pressto receive land ltransmit the fluid which leaks into the interior of the cap 12 past the valve plunger 62. Thus, each safety valve 5I may be adjusted to discharge pressure fluid at adiiferent predetermined pressure by differently adjusting the adjusting screw 11 to compress the springs 14 by different amounts. The clamping member 44 is provided Figures l and 2, the pump 39 is started and deact. It will be seen from Figures 1 and 2 that 75 livers pressure iluid to the four-way valve 2l, which in turn', is set to deliver pressure duid through'the line 25 and port 24into the space above theV drawing plunger head 23. This prese sure forces the drawing plunger 22 and platen 35 downwardly, carrying with them the clamping member 44. When the latter engages the 'poriphery oi" the blank I5 and clamps it tightly against the die memberl I4, the clamping member 44 halts,` but the platen 35 continues to -move downwardly. forcing its drawing die or punch 4I seting of each relief valve Il.

ters Patent is: e 1. In combination in a drawing press, a main into engagement with the blank II. As the punch Il moves downwardly it forces the central portion of the blank ,It into the die cavity I! and overcomes the resistance of the supporting plunger Il, whichv protects the tip of the work piece or blank I8. i

Meanwhile pressure has been built up in the clamping cylinders 31 by reason of the relative motion between the platen 28 and the clamping member 4l to which the clamping plungers 3l are attached, and the fluid 'in the clamping cylinders 21 has been prevented from escaping by the closing of the outwardly opening check valves 46. When the pressure within each clamping cylin'- der 31 reaches the amount for which its corresponding relief valve 5I is set, the latter opens and drawing plunger for generating iluid pressure to .actuate said clamping plungers after said clamp'- in'g plungers have been brought to rest by the engagement of said clamp with the work piece on said work piece support to clamp the work piece during the drawing operation, and an individual pressure relief device associated with each clamping cynnder and adjustable to an individual pressure for discharging fluid from said clampdischarges fluid through the line 53, into the dis- .i charge line 52 leading to the telescoping cylinder il, and thence by the line 55 to the surge tank I8. In this manner each clamping plunger 38 may be caused to exert a'diilerent force upon the portion of the blank periphery which is engaged by the clamping member Il in its vicinity.

When the drawing stroke of the press has been completed the -setting of the four-way valve 28 is reversed so that pressure uid ows through the.

line 21 and port 25, into the space beneath the drawing plunger head 23, causing the drawing plunger 22 to move upwardly. A portion of this pressure fluid, however, passes downwardly through the plunger passageway Il. the -outwardly opening relief valves IB, to the passageways IB, into the clamping cylinders`31, causing their plungers 38 and the' clamping member Il to remain in clamping engagement with the blank i6 while the punch or drawing die Il is withdrawn from the cavity I5 of the die Il. If the relief valves il have been set for-,a low clamping, pressure it would, at i'lrst glance, seem that pressure fluidduring the pull-back stroke would pass from the clamping cylinders 48, through the relief valve 5I' and lines 52, 53 and 55, back into the surge tank I9, thus preventing the return of the moving parts. This, however, is prevented by the operation of the pipe line Il leading from the valve cap 12 of the valve 5I to the passageway 41 within the drawing plunger 22. pressure is applied simultaneously upon opposite sides of the valve plunger 02 within the relief valve 5l, and prevents its opening regardlessof how low a clamping pressure is provided by the When the platen 38 has moved upwardly along the rods Il it will `engage the nuts lll and lift -the clamping member l2 free from engagement with the work piece I6,

- thereby enabling the operatorio remove the work piece and also lifting the entire platen and blankholder assembly as a unit.

It will be understood that I desireto comprethe claims andk the invention. 1

Having thus fully described my invention, what I claim as new and desire to secure by Lettached to said clamping plungers, said clamping v cylinders being responsive to the motion of said Consequently, during the pull-back stroke ing cylinder in response to the attainment of a predetermined pressuretherein, said clamping 'cylinders being connected with. the return side of said drawing plunger for maintaining said clamping plungers in clamping engagement with the work piece during the nrst part of the re- Vturn stroke of said drawing plunger, and 'a lplurality of check valves respectively associated with said clamping cylinders for permitting the flow of fluid to said clamping cylinders from' the returnv side -of said drawing plunger but adapted to prevent ilow of fluid in the opposite direction.

2.' In combination in a drawing press, a press bed, a work piece'support thereon, a drawing cylinder. a double-acting drawing plunger therein,

a platen operated by said drawing plunger, clamping cylinders lmounted on said platen,

clamping pistons in said clamping cylinders, a

clamping member attached to said clamping pistons, said clamping cylinders being responsive to the motion of said drawing plunger for generating nuid pressure to actuate said clamping pis- Y j tons after said clamping pistons have been `.hend within this invention such modifications as come within the scope of hydraulbrought to rest by the engagement of said clamp-- ing member with the work piece on said work piece support, said drawing cylinder and said clamping cylinders being hydraulicallylinterconnected by fluid-conducting means extending from the return side of said drawing cylinder to said clamping cylinders for conveying fluid therebetween, a pressure relief device connected to each clamping cylinder for discharging pressure therefrom in response tothe attainment of a predetermined pressure therein, and means connecting said pressure relief devices to the return side of said drawing cylinder for rendering said pressure relief devices inoperative during the return stroke of said drawing plunger.

3. In combination in a drawing press, a press bed, a work piece support thereon, a drawing,

cylinder, a double-acting drawing plunger therein, a platen operated by said drawing plunger, clamping cylinders mounted on said platen. clamping pistons in said clamping cylinders, a. clamping member attached to said clamping pistons, said clamping cylinders being responsive to the motion of said drawing plunger for generating fluid pressure to actuate said lclamping pistons after said clamping pistons have been brought to rest by the engagementof said clamping member withthe work piece on said work piece support, said drawing cylinder and said clamping cylinders being hydraulically interconnected by fluid-conducting means extending from the return side of said drawing cylinder to said clamping cylinders for conveying fluid therebetween, a pressure relief device connected to each clamping cylinder for discharging pressure therefrom in response to the attainment of a predetermined pressure therein, means connecting said pressure relief devices to the return side of said drawing cylinder for rendering said pressure relief devices inoperative during the return stroke of said drawing plunger, 'and unidirectional valve means associated with the fluid-conducting means for peignitising the ilow of fluid' said clamping cylinders to the to said clamping cylinder from the return side of said drawing plunger but adapted to prevent the flow of iluidin thel opposite direction to maintain the clamping action ofV the clamping plungers during thereturn stroke of said drawin'g'plungers.

4. In combination in a press, a drawing cylinder, a double-acting drawing plunger therein, a platen operated by said drawing f plunger, a plurality of clamping cylindersfin saidplaten, clamping plungers in said clampin'g'cylinders, a clamping member attached 'to said clamping plungers and adapted to be operated by the relative motion between said clamping cylinders and said clamping plungers, a plurality' of pressure relief valves adjustable to differ-entreleasing pressures, one pressure relief valve being connected to each clamping cylinder for discharging pressure iluid therefrom in response to the attainment of a predetermined pressure therein, fiuidpassageways interconnecting said clamping cylinders and the' return side of said drawing plunger for conveying iluid to said clamping cylinders to maintain the clamping action of the clamping plungers' and hold the clamping members in engagement with the work piece at the start of thereturn stroke of the drawing plunger, and a plurality of check valves ing cylinder, a double-acting drawing plunger therein, a platen operated by said drawing plunger, a plurality of clamping, cylinders in said platen, clamping plungers in said clamping cylinders, a clamping member attached to said clamping plungers and adapted to be operated bv the relative motion between said clamping cylinders and said clamping plungers, a plurality 4of pressure relief valves adjustable to different releasing pressures, one pressurerelief valve 'being connected to each clamping cylinder for discharging pressure fluld therefrom in. response to the attainment of a predetermined pressure therein, fluid passageways interconnecting said clamping cylinders and the return side of said drawingv plunger for conveying fluid to said clamping cylinders to maintain the clamping action of the clamping plungers and hold the 'clamping member in engagement with the work piece at the start of the return stroke of the drawing plunger,

and check valves in each of the respective passageways for preventing the ilow of iuidvfrom return side of said drawing plunger.

(i. In combination in a drawing press, a main' cylinder, a main plunger, a platen operated theresalsa said work piece support, an adjustable pressure relief valve for each clamping cylinder arranged to discharge pressure nuid individually from each clamping cylinder at a predetermined pressure ldiffering from. the discharge pressure in at least one of the other clamping cylinders, and means interconnecting said pressure relief valves with the return side ofsaid main plunger for rendering said pressure relief valves inoperative during the return stroke of said main plunger.

7. In combination in a drawing press, a main cylinder, a main plunger, a platen operated thereby, a press bed, a work piece support thereon, a plurality of clamping cylinders mountedon said platen, clampingplungers operating therein. a clamp attached tosaid clamping plungers, said ,v clamping cylinders being hydraulically connect- Vedto the return side oi said main cylinder whereby to .maintain theclamp in engagement with the workpiece during the iirst part of the return stroke of said main plunger, said clamping cylinders being responsive to the motion of said main plunger for 4generating uid pressure to actuate said clamping plungers after said clamping plungers have been brought to rest by the engagement of said clamp with the work piece on said work piece support, an adjustable pressure relief vvalve for each clamping cylinder arranged to discharge pressure fluid individually fromeach clamping cylinder 'at a predeterminedv pressure differing from the discharge pressure in at least one of the'other clamping cylinders, and a conduit extending from said pressure relief valves to the return side of said main plunger, said pressure relief valves including means for rendering said pressure relief valves inoperative during the return stroke of said main plungers.

. 8. In combination in a drawing press, a press bed, a work piece support thereon, a drawing cylinder, a double-acting drawing plunger therein. a platen operated by said drawing plunger, clamping cylinders mounted on said platen,

clamping pistons in said clamping cylinders, a

. said clamping pistons have been brought torest by, a press bed, a, work piece support thereon, a Y

plurality of clamping cylinders mounted on said platen, clamping plungers operating therein, a clamp attached to said clamping plungers, said clamping cylinders being hydraulically connected to the return side of said main cylinder whereby tov maintain the 4clamp in engagement with the work piece during the iirst part of the return stroke of said main plunger, said clamping cylinders beingresponsive to the motion of said main plunger for generating duid pressure to actuate said clamping plungers after said clamping plungers have been brought to rest by the ngagement ofv said clamp with the work piece by the engagement of said clamping member with the work piece on said work piece support, a pressure reliefdevice connected to each clamping cylinder for discharging pressure therefrom in responseto the attainment of a predetermined pressure therein, and means connecting said pressure relief devices to the return side of said drawing cylinderfor rendering said pressure relief devices inoperative during the return stroke of said drawing plunger'.

9. In combination inla press, a press phmger ,Operable to shape a work piece, a plurality of clamping cylinders movably connected to said press plunger, clamping plungers respectively reciprocable in said cylinders, a clamping member attached4 to said clamping plungers andV operable to engage said work vpiece and to clamp the same against a support, means for conveying fluid to said clamping cylinders, said clamping cylinders being responsive to the movement of said press plunger toward said work piece, while thelatter isenllsed bysaidclampingmembcr.

for creating pressure in said clamping cylinders, means responsive to pressure thus created in said clamping cylinders for preventing equalization of pressure in saidl clamping cylinders, and means respectively connected to said clamping cylinders and adjustable independently of each other for at the same time maintaining predetermined different pressures in at least two clamping cylinders.

10. In combination in a press, a reciprocable press plunger, a platen movable by said press plunger. a plurality of clamping cylinders in said platen, clamping plungers corresponding in number to said clamping cylinders and reciprocable therein, a clamping member attached to said clamping plungers and operable to exert clamping pressure on a work piece to be shaped, to

hold the same clamped against a support during the shaping of said work piece uid conveying means for conveying iluid to said clamping cylinders, said clamping cylinders vbeing'responsive to the movement of said platen toward said clamp- Iing member for creating pressure in said clamping cylinders, means responsive to pressure thus created in said clamping cylinders for lnterruptf cylinders mounted on said platen, fluid operable clamping plungers in said clamping cylinders, a clamp attached to said clamping plungers, said clamping cylinders being responsive to the movement of said drawing plunger for generating fluid pressure to actuate said clamping plungers after said clamping plungers have been brought to rest by the engagement of said clamp with a work piece on said work piece support, to clamp the work piece during the drawing operation, and pressure relief devices respectively associated with said clamping cylinders and adjustable independently of each otherto an individual pressure for discharging iiuid from the respective cylinder in response to the attainment of a prev determined pressure therein.

ing hydraulic communication between said fluid v for discharging pressurefluid individually from work piece to be shaped, a plurality of clamping 12. In combination in` a press, a reciprocablc pressing platen, a plurality of clamping cylinders on said platen, uid operable. clamping plungers operating in said clamping cylinders, a clamping member attached to said clamping plungers for clamping a work piece to .be shaped, said clamping cylinders being responsive to the movement of said pressing platen for generating fluid pressure to actuate said clamping plungers after said clamping plungers` have been brought to rest by the engagementof said clamping member withV the work piece to be shaped, a plurality of pressure relief devices individually adjustable to different releasing pressures, one pressure relief devicebeing connected to each clamping cylinder each clamping cylinder at a predetermined pressure diiering from the discharge pressure in at least one of the other clamping cylinders, and means adapted to make said pressure relief devicesineffective during the return stroke of said pressing platen.

. f WALTER ERNST. 

